OSU offers tips for managing diseases of tomatoes, potatoes and cucumbers

July 12, 2010

Late blight and downy mildew - diseases that attack tomatoes, potatoes and vine crops such as cucumbers and squash - have been confirmed in Ohio, threatening vegetable farms and backyard gardens across the state.

"Whatís different this year is that both diseases have appeared in Ohio earlier than we have seen before," said Sally Miller, vegetable pathologist with Ohio State University Extension.

If left unmanaged, both downy mildew and late blight - which are transmitted via spores - can result in complete destruction of crops. Recent rainy and stormy weather most likely created favorable conditions for these diseases to show up in Ohio, since their spores are carried by winds and they thrive in wet environments.

Downy mildew was found June 23 on cucumbers in Wayne and Holmes counties (northeast Ohio), following reports of the disease in Ontario, Canada, the previous week.

Late blight was confirmed around the same time on tomatoes on an organic farm in Harrison County (east-central Ohio). This follows confirmations of late blight in potatoes, tomatoes or both in Michigan, Pennsylvania, Kentucky and New York.

"People need to be on the alert for these diseases and prepare for their possible arrival on farms or gardens," Miller said.

Detailed management recommendations for both diseases are available at

Ohio State fact sheets with photos of symptoms and additional disease information can be found at (downy mildew) and (late blight).

A video about late blight is available at

Organic farmers wanting to learn more about late blight can register for a free webinar that will take place this Thursday, July 1, at 8 p.m. EST, courtesy of eXtensionís eOrganic educational tool. Go to for more information and registration details.